Color Vision Test
How to Use
This tool generates pseudoisochromatic plates (Ishihara-style) using Canvas. Each plate hides a number among colored dots. People with normal color vision can read it, while those with color vision deficiencies cannot. View each plate, select the number you see, and get your result after completing all plates.
What is Color Blindness?
Color blindness (color vision deficiency) occurs when one or more types of cone cells in the eye are missing or dysfunctional, making it difficult to distinguish certain colors. In 1794, English chemist John Dalton was the first to systematically describe this condition — he was red-green colorblind himself, which is why color blindness is still called "Daltonism" in many languages. Dalton documented his confusion between red and green, hypothesizing (incorrectly) that it was due to discoloration of the eye's vitreous humor, but he pioneered the scientific study of color vision.
Color blindness is far more common in males than females: about 8% of males and only 0.5% of females are affected. The reason lies in genetics — the genes for red and green cone photopigments are on the X chromosome, making color blindness an X-linked recessive trait. Males have only one X chromosome (XY), so a single defective gene is enough to cause color blindness. Females have two X chromosomes (XX), so they need defective genes on both copies to be affected — otherwise the normal copy compensates.
Protanopia (Red-blind)
Missing L-cones (long-wavelength). Cannot perceive red light. Affects ~1% of males. Reds appear dark and greenish.
Deuteranopia (Green-blind)
Missing M-cones (medium-wavelength). Cannot distinguish red from green. Affects ~1% of males. The most common type.
Tritanopia (Blue-blind)
Missing S-cones (short-wavelength). Cannot distinguish blue from yellow. Very rare, affects males and females equally (not X-linked).
Achromatopsia (Total color blindness)
All cone cells are absent or nonfunctional — only grayscale vision. Extremely rare (~1 in 30,000), often accompanied by photophobia and low visual acuity.
About the Ishihara Test
The Ishihara color vision test was designed by Japanese ophthalmologist Dr. Shinobu Ishihara in 1917 at the University of Tokyo. The Japanese military needed a quick and reliable method to screen conscripts for color vision deficiencies, and Ishihara was tasked with developing one. His design uses pseudoisochromatic plates — circular cards filled with dots of varying sizes and colors, with a hidden number formed by dots of a different color.
The design works because it exploits confusion lines in CIE color space — lines along which color-deficient individuals cannot distinguish between colors. For red-green colorblind people, the red-toned and green-toned dots on a plate appear identical in hue and brightness, making the hidden number invisible. People with normal color vision easily see the contrast.
The Ishihara test remains the most widely used color vision screening method worldwide. The original set contains 38 plates designed to detect red-green deficiency. This tool simulates the principle by generating similar pseudoisochromatic plates programmatically using Canvas.
Color Vision Science
Human color vision relies on three types of cone cells in the retina, each sensitive to different wavelengths of light:
- S-cones (Short): Sensitive to blue-violet light, peak ~420nm
- M-cones (Medium): Sensitive to green light, peak ~530nm
- L-cones (Long): Sensitive to red-yellow light, peak ~560nm
This is the Trichromatic Theory (Young-Helmholtz theory). It was first proposed by English polymath Thomas Young in 1802, who hypothesized that just three types of "color-sensing fibers" could account for all color perception. Fifty years later, German physicist Hermann von Helmholtz refined and experimentally validated the theory in 1852. Every color we perceive is the brain's interpretation of the ratio of signals from these three cone types — when one or more cone types are missing or abnormal, color vision deficiency results.
Related Tools
- Color Format Converter — Convert between HEX, RGB, HSL, HSV
- Color Contrast Checker — Check WCAG contrast ratios for text and backgrounds
- Color Blindness Simulator — Simulate how colorblind people see colors
- Accessible Color Pairs — Find WCAG-compliant color combinations
- Color Palette Generator — Generate harmonious color schemes
Frequently Asked Questions
No. This is a screening tool only. Screen color reproduction, brightness settings, and ambient lighting can all affect results. The real Ishihara test uses professionally printed, standardized plates under controlled lighting. If this tool suggests you may have a color vision deficiency, please visit an ophthalmologist for professional testing.
Because the genes for red and green cone photopigments are located on the X chromosome. Males have an XY sex chromosome combination with only one X, so a single defective gene causes color blindness. Females have XX — both copies need to be defective for color blindness to manifest, which is far less likely. A female with one defective copy is called a "carrier" — she has normal color vision but can pass the gene to her children.
Currently, there is no proven cure for inherited color blindness. Special filter glasses like EnChroma can enhance contrast for certain colors, helping some color-deficient individuals distinguish them better, but they do not truly restore missing color vision. Gene therapy has shown success in animal models (successfully tested in squirrel monkeys in 2009), but human clinical application remains distant. Acquired color vision deficiency (caused by medication or disease) can sometimes be reversed once the underlying cause is addressed.
In most countries, people with mild to moderate red-green color blindness can obtain a regular driver's license. Traffic lights have a fixed position arrangement (red on top/left, green on bottom/right) in addition to colors, so colorblind drivers can use position to determine the signal. However, certain specialized licenses (such as pilots or train operators) may require passing a color vision test. Regulations vary by jurisdiction — check your local requirements.
Different displays have varying color gamuts (sRGB, DCI-P3, etc.), color calibration, brightness settings, and panel types (IPS, VA, OLED, etc.), all of which affect how colors are rendered. The same pseudoisochromatic plate may look completely different on an uncalibrated display versus a calibrated one. For the most reliable results, use a well-calibrated display, test under normal indoor lighting, and set screen brightness to a moderate level.